Ab initio investigation of optical properties of As2S3 and Ag doped As2S3

Abstract The density functional theory along with generalized gradient approximation is used to calculate the optical properties of As2S3 and Ag0.25As1.75S3. The effective band gap of Ag0.25As1.75S3 is reduced as compared to As2S3. The scissor correction of 1 eV is used to calculate the optical properties. The dielectric function of Ag0.25As1.75S3 enhances significantly at low energies while at higher energies there is constant shift in the peak positions of Ag0.25As1.75S3 as compared to As2S3. Similar enhancements at low energies and shift at higher energies are found in the refractive index, optical conductivity, absorption coefficient and reflectance of Ag0.25As1.75S3 as compared to As2S3. The optical parameters are found more anisotropic at low energies however at higher energies the anisotropy nearly vanishes. The Ag0.25As1.75S3 is found more birefringent than As2S3. The calculated results closely agree with the available experimental estimates of crystalline, amorphous and thin films of As2S3 and Ag0.25As1.75S3.